Fuel injection devices, such as fuel injectors, fuel pumps, and the like, typically include mechanical, spring-loaded elements for pressurizing fuel. For example, and with reference to FIG. 1, some fuel injectors 10 are mechanically actuated via a rocker arm assembly 14 that moves with each rotation of an engine's cam shaft 18. The rocker arm assembly 14 moves a tappet 22 and a plunger 24 downward to pressurize fuel within a fuel cavity inside the fuel injector 10. Pressure within the fuel cavity builds until a threshold pressure is reached. Once the threshold pressure is reached, the injector 10 opens at its forward end 32 to expel pressurized fuel from the fuel cavity. As fuel is expelled, pressure within the fuel cavity decreases rapidly, causing the tappet 22 and the plunger 24 to accelerate downward. A compression spring 26 acts upon the tappet 22 and the plunger 24 to offset the downward acceleration of the tappet 22 and the plunger 24 and to return them to their pre-injection positions.
During operation of the fuel injector 10, the compression spring 26 is subject to dynamic loading, which can create internal oscillations in the spring 26. Such oscillations, or “surge modes”, may cause undesirable conditions within the fuel injector 10, such as increased dynamic stress within the spring 26 and clashing between adjacent spring turns 28 or between a spring tang 29 (i.e., an end turn) and an adjacent turn 28. Such conditions may ultimately cause spring failure within the fuel injector 10. Thus, prior art fuel injector devices may be improved by providing means for reducing such conditions.
The present invention is directed at overcoming one or more disadvantages associated with prior fuel injector springs.